Hotmelt adhesives, which are suitable for bonding a very wide range of materials, are known in general. US 2004/0077759 A1 describes hot co-extrudable self-adhering hotmelt adhesives that are particularly suitable for the production of multi-layer films for use in resealable packaging products. Films of this type comprise at least three layers: a first, outer layer, a sealing layer, which defines the inner side of the packaging product, and therebetween a resealable hotmelt adhesive layer. The described adhesives include tackifying resins and specific styrene-block-copolymers in precisely defined amounts.
By contrast with this disclosure, the present invention solves the application requirements based on an SIS polymer system that manages with a small fraction of SIS in the total formulation and also uses SIS block polymers having a diblock fraction of less than 30%, preferably less than 20%. The described adhesive system can be processed by extrusion and thus can be directly integrated in the production process for resealable packaging products.
In the case of resealable packaging products, the adhesive plays an important role insofar as the quality of the resealing and renewed opening are very substantially dependent on the adhesive properties. The adhesive must be self-adhering, i.e. the tackiness is attained by simply being pressed on by hand. These adhesives are known as PSAs (pressure-sensitive adhesives).
Hotmelt adhesives of this type must also have cohesion properties which, during the opening of the packaging products coated therewith, promote a cohesive separation, i.e. a separation within the adhesive layer whilst adhesive remains on both opened carrier materials. By contrast, an adhesive separation, i.e. a separation along the boundary layer between adhesive and carrier material, can be undesirable.